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Björn Norén
9,569 PointsJava Multiply big numbers Question
Hi! If I multiply 300 * 1000 * 1000 * 1000 in Java I get the number: -647710720 Could someone explain why it isn't 300 000 000 000?
I use cmd.exe
Here's the code:
public class Test
{
public static void main (String[] args)
{
System.out.println(300 * 1000 * 1000 * 1000);
}
}
Jeremy Hill
29,567 PointsLike this:
public class Test{
public static void main (String[] args)
{
long num = 300L * 1000L * 1000L * 1000L;
System.out.println(num);
}
}
3 Answers
Ken Alger
Treehouse TeacherBjorn;
That is a great question.
In looking at some of the limitations on number types Java has, you will see that the int data type is a 32-bit signed two's complement integer. It has a maximum value of 2,147,483,647(inclusive), (2^31 -1).
For your code above, you will want to utilize a data type which allows for a larger range. If you use the longdata type it is a 64-bit signed two's complement integer. It has a maximum value of 9,223,372,036,854,775,807 (inclusive), (2^63 -1) and used by designating the number as a Long type with the L character. You can add that to one of the numbers in your equation and the entire number will be converted to a Long type. For example:
public class Test
{
public static void main (String[] args)
{
System.out.println(300 * 1000 * 1000 * 1000L);
}
}
Post back with further questions.
Happy coding, Ken
Björn Norén
9,569 PointsHi Ken, thanks for reaching out and helping me, I appreciate it alot!
I apologize, I should have emphazied that I wonder WHY it results in such a random number, and that I know that it should be utilized to a long, for example. So, is this a way for Java to say that the number -647710720 equals 300 000 000 000, when defualted to a double? Is that accurate?
Philip Gales
15,193 PointsIt is defaulting to a double, which is why it always shows that random number. Try explicitly telling it that it is a long.
//long x = 300L * 1000L * 1000L * 1000L;
long x = 300 * 1000 * 1000 * 1000;
System.out.println(x);
You may notice I have 2 lines with 1 commented out. Even though I have assigned both to a long, without the "L" telling java each number is a long it will still multiply as if it were a double.
Philip Gales
15,193 PointsFor anything large like 50 digit or more you can use a BigInteger.
Björn Norén
9,569 PointsHi everyone, thanks for reaching out and helping me, I appreciate it alot!
I apologize, I should have emphazied that I wonder WHY it results in such a random number, and that I know that it should be utilized to a long, for example. So, is this a way for Java to say that the number -647710720 equals 300 000 000 000, when defualted to a double? Is that accurate?
Jeremy Hill
29,567 PointsJeremy Hill
29,567 PointsI don't know why it gave that output but I do know that you should use type Long for big numbers.